The gut microbiome in early age-related macular degeneration

The gut microbiome is implicated in the development of advanced age-related macular degeneration (AMD) but no study has investigated microbial composition in early AMD nor controlled for important microbiome modulators such as diet and light. This is crucial as diet can change the microbiome rapidly as well as affects disease progression. In addition, the light signalling photoreceptors are dysfunctional in AMD. Here we determined the gut microbiota by conducting 16S DNA metagenomic sequencing of 40 faecal samples from 20 participants with and without early AMD. We normalised both groups to the same diet over 5 days and determined gut microbial composition before and after the diet. To control for light, we assessed habitual light exposure with actigraphy and the post-illumination pupil light response (PIPR) quantified photoreceptor signalling. Clostridium termitidis, Bacteroides gallinarum, and Bacteroides finegoldii were significantly abundant in early AMD compared to controls at both time points. Interestingly, pro-inflammatory species such as Sutterella were only significantly abundant in AMD before the diet. After the diet, the gut microbiome shifted to a significantly greater abundance of commensal bacteria in AMD. Controls and AMD patients had a similar ambient light exposure, however the PIPR was significantly reduced in AMD suggesting impaired light signalling. We are the first to show a distinct gut microbiome in early AMD and infer that dietary changes may positively affect the gut microbiome at early stage of the disease.